1. Field of the Invention
The present invention relates to a process for producing an ink jet head.
2. Description of the Related Art
An ink jet head applied to an ink jet recording system generally has an ink flow path, an energy-generating portion provided in a part of the ink flow path, and minute ink ejection orifice for ejecting an ink by the energy of the energy-generating portion. As a process for producing such an ink jet head, is known a process disclosed in, for example, Japanese Patent Publication No. H06-45242. According to this process, an ink flow path pattern which will become a mold of an ink flow path is formed with a photosensitive resin material on a substrate on which energy-generating elements have been formed as an energy-generating portion. A coating resin layer which will become a nozzle material is formed on the substrate so as to coat the ink flow path pattern. Ink ejection orifices communicating with the ink flow path pattern are formed in the coating resin layer. Thereafter, the ink flow path pattern is removed to form the ink flow path, thereby producing an ink jet head.
Japanese Patent Application Laid-Open No. H06-286149 discloses that a positive resist composed of a vinyl ketone type photodegradable polymer compound such as poly (methyl isopropenyl ketone) or poly(vinyl ketone) is used as the photosensitive resin material for forming the ink flow path pattern. Such a positive resist is polymeric and is hence excellent in resistance to a solvent upon the coating and formation of the coating resin layer which will become a nozzle material and hard to cause pattern break down. In addition, the molecular weight of this resist is lowered by light irradiation upon the removal of the ink flow path pattern, and so the resist can be easily dissolved and removed with an organic solvent.
On the other hand, with the miniaturization of semiconductor integrated circuits in recent years, attention is paid to a double patterning method in which patterning is repeated twice as a method for obtaining a fine resist pattern. In this method, a patterned resist is coated with a resist again to repeat the patterning, so that the resist first patterned is required to have solvent resistance. As a method for imparting the solvent resistance to the resist pattern, is disclosed a method in which a compound having an isocyanate group or a functional group which forms an isocyanate group by heating is applied to the surface of a pattern formed of, for example, a chemically amplified positive resist, followed by baking (Japanese Patent Application Laid-Open No. 2009-15194).
However, the positive resist composed of the vinyl ketone type photodegradable polymer compound such as poly(methyl isopropenyl ketone) or poly(vinyl ketone) requires a lot of energy for its degradation reaction and thus has extremely low sensitivity. On the other hand, an alkali-developing positive resist containing a resin such as polyhydroxystyrene or phenolic novolak as a main component is a resist which forms an image by utilizing a polarity change and thus is high in sensitivity and resolution. Therefore, such a resist is widely used in the field of semiconductors. However, the alkali-developing positive resist is low in solvent resistance because it contains the resin having a phenolic hydroxyl group as the main component. Therefore, when such a resist is applied to the material of the ink flow path pattern in the production of the ink jet head, pattern break down may be caused in some cases upon the coating and formation of the coating resin layer which will become the nozzle material. Since the chemically amplified positive resist has extremely high sensitivity and excellent resolution, it is suitable for use as a material for forming the ink flow path pattern in the production of the ink jet head. When a pattern formed of the chemically amplified positive resist is treated by utilizing a chemical reaction by the isocyanate group according to the method described in Japanese Patent Application Laid-Open No. 2009-15194, a cured component is formed on the surface of the resist pattern, and so the resistance to the solvent upon the coating and formation of the coating resin layer which will become the nozzle material becomes sufficient. However, it is difficult to dissolve and remove this resist pattern with an organic solvent. This is because the cured component formed on the surface of the resist pattern does not cause a photo-degradation reaction and thus is low in solubility in organic solvents.